Availability zones

This is a relatively new concept introduced in Azure and is very similar to zone redundancy for storage accounts. Availability zones provide high availability within a region by placing VM instances on separate data centers within a region. Availability Zones are applicable to VMs, managed disks, VM scale sets, and load balancers. This constituted a gap in Azure for a long time and it was removed recently, from a computing high-availability perspective, which was removed recently. 

Each Azure region comprises multiple data centers. Some regions have more data centers, while some could have less; however, there are at least two data centers in every region. These data centers are known as zones. Deploying VMs in an availability zone ensures that those VMs are in different data centers and obviously are on different racks and networks, and so on. These data centers in a region relate to high-speed networks and there is no lag in communication between these VMs.

If an application needs higher availability and wants to ensure that it is available even if an entire Azure region is down, the next rung of the ladder for availability is the traffic manager feature, which will be discussed later in this chapter.